One possible scenario in this fanfiction could be that Vampire Rosario Mizore and Sub Zero find themselves in a strange, new realm. Maybe they initially see each other as threats due to their very different natures. Mizore, being a vampire, has her own set of powers like enhanced speed and the ability to charm, while Sub Zero has his ice - based powers. However, as the story progresses, they might realize they can help each other in some way, perhaps to defeat a common enemy that threatens both of their worlds.
In a fanfiction, Mizore might be accidentally transported to the Mortal Kombat realm where she meets Sub - Zero. At first, Sub - Zero is suspicious of her as she is an unknown entity. However, Mizore's shy and somewhat naive nature starts to soften Sub - Zero's tough exterior. They could then go on a journey to find a way to send Mizore back home, while also having adventures and fighting off various threats along the way.
They could have an epic battle. Sub - Zero's combat skills from Mortal Kombat and Mizore's speed and stealth from Rosario Vampire would make for an exciting fight. Maybe it starts because of a misunderstanding, like Sub - Zero thinking Mizore is a threat to his clan.
Well, one possibility could be that Tsukune, being a vampire in the Rosario Vampire universe, somehow gets involved with the Sub Zero world. Maybe he has to face off against Sub Zero's enemies using his vampire powers. For example, he could use his super strength and speed to combat the ice-based attacks of Sub Zero's foes.
The plot could involve a quest. Maybe there is a powerful artifact that has been lost, and both Mizore and Sub Zero are somehow connected to it. Mizore might need the artifact to gain more power in the vampire world, and Sub Zero could be on a mission to keep it out of the wrong hands. Their paths cross, and at first, they are at odds. But as they learn more about the artifact and the forces that are after it, they join forces. For example, they might have to fight off demons who also want the artifact.
Tsukune could fit in as an outsider with unique abilities. His vampire powers would be a contrast to the ice - based powers in the Sub Zero world. He might be initially seen as a threat or a curiosity.
I'm not sure if there is such a specific fanfiction where a character from Rosario Vampire is reading Naruto fanfiction. Fanfiction can be very diverse, but this seems like a rather unique and specific concept. It's possible that it might exist in the vast realm of fan - created stories, but it would be quite difficult to find without a more targeted search.
One possible fanfiction could involve a crossover between Rosario Vampire and Arrancar. The unique powers and characteristics of both vampires and arrancar could create interesting plotlines. For example, a Rosario Vampire character might encounter an arrancar and initially mistake them for a normal vampire. This could lead to a series of misunderstandings and battles as they figure out each other's true nature.